1. Field of the Invention
The present invention relates to bonding tools of the type used in automatic wire bonding machines and tape automated bonding machines to make electrically conductive interconnections between the pads on a semiconductor device and the leads on a frame or carrier. More particularly, the present invention relates to adding a very thin hard coating of amorphous ceramic material to the working face of known bonding tools so that the original specifications and tolerances are preserved and the working face is improved in smoothness and hardness.
2. Description of the Prior Art
Bonding tools used to make fine wire interconnection on semiconductor devices are commercially produced as capillary bonding tools or as wedge bonding tools. By far the larger percentage of such tools are capillary bonding tools. Either type tool may be modified to produce a single point bonding tool of the type used to connect a prefabricated flexible pattern of leads to pads on a semiconductor device in a process called the tape automated bonding or TAB. Each of the three types of tools have been made in more than one type of working face in order to solve different problems.
A current problem is excessive wear of the working face of each bonding tool used for very small bonding pads on a semiconductor device. The pads are presently smaller than 3.0 mils square on high density computer chips of the type which typically drive the state of the art. The next generation computer chip will have 2.0 mil square pads. The bonding tools used to make wire bonds or TAB bonds on these pads must have a working face that does not extrude or expand the bond being made over the edges the pads. This requires that the tip diameter (T) of the fine pitch bonding tool be made about the size of the pad and that the working face which extrudes the wire or tab lead be effectively smaller that than the fine pitch pad size or under 3.0 mils.
The above requirements, when imposed on fine pitch bonding tools have resulted in smaller working faces on high speed bonding tools of the type shown and described in U.S. Pat. Nos. 5,421,503 and 5,558,270 that are assigned to the assignee of the present invention. It was found that the mean time before replacement of these prior art tools has been reduced by over 50% and the next generation of fine pitch bonding tools will have a further reduced operational life.
It would be desirable to provide capillary or wedge type bonding tools which can be made on existing production machinery using existing materials and methods of manufacture that can be further processed in a manner which more than doubles the operational life of the bonding tool.